Behavioral Theories of Motor Control

Chapter 3

Overview

Now that we’ve looked at response preparation, what happens during the response programming stage?

Early Motor Program Theories

Proposed that for each movement to be made, a separate motor program existed and was stored in memory

Two problems:

– Storage: Hard drive (brain) could run out of space

– Novel responses: How do you respond to an action never done before?

Command Center

Decision> appropriate plan retrieved from memory> instructions to rest of body for action

Open Loop Systems

Open loop

– Action plans generated by command center then carried out by the limbs and muscles without modification

Command Center Action

Mechanical Example:Sending Email

Closed Loop Systems

Closed loop

– Command center generates action plan that initiates the movement

– Feedback is used to modify on-going action

Command Center

Action

Feedback

Mechanical Example: Thermostat

Slow Vs. Rapid Movements

Motor control uses both open and closed loop systems

– Movements are planned in advance, initiated & executed with little modification (remember the fake in PRP?)

– If a rapid movement, feedback will be used for the next attempt

– For slower movements, open loop begins the movement and closed loop will continue to completion

Problem:

How does a person do a novel motor skill?

Motor Program

– Abstract representation of a movement plan

– Stored in memory

– Issues instructions that are carried out by the limbs and muscles

Generalized Motor Program (GMP)

Represents a class of actions or pattern of movement that can be modified to yield various response outcomes

Invariant features

– Relatively fixed underlying features that define a GMP

Parameters

– Flexible features that define how to execute a GMP

Fixed vs. Flexible Features

Write your name with the following:– Your dominant hand– Your non-dominant hand– Pen in your mouth– Pressing very hard– Pressing very soft– Write quickly, then slowly

Which aspects were fixed? Flexible?

Invariant Features

Relatively fixed underlying features

– Sequence of actions or components

– Relative timing Internal rhythm of the skill : the amount of time to write each letter

of your name will stay the same whether writing fast or slow

– Relative force Internal force relationship: The amount of force given to write each

letter stays proportionally the same whether pressing hard or soft

Parameters

Adaptable features of program

Easily modified from one performance to another to produce variations of a motor response

– Overall duration: Fast or slow

– Overall force: Hard or soft

– Muscle selection: Writing with hand or foot?

Review Question

When swimmers use hand paddles or when baseball hitters swing heavier bats, does this manipulate invariant features or parameter features?– When might such an action hinder the development

of correct technique?– What signs would you look for to avoid this

problem?

Schema

Rule or relationship that directs decision-making when a learner is faced with a movement problem

Developed by abstracting 4 sources of information for each performance attempt

1. Initial conditions present at start of movement

2. Response specifications: parameters used in the execution of the movement

3. Sensory consequences: what did the action feel like?

4. Response outcome: how successful was the response?

Schema Development

For each movement attempt the four sources of information are stored in memory briefly

Feedback from the attempt verifies– How successful was the performance?– Do I need to change the movement?

With each additional attempt, the strength of the schema increases when you compare one attempt to the next

Motor Response Schema

Recall schema

– Responsible for organizing the motor program What do I need to do?>What conditions exist?>What

parameters & invariant features are required?>Execute the response

Recognition schema– Responsible for the evaluation of a movement attempt :

Was the movement correct?

Error signal updates the recall schema

Dynamic System Theory

Movement pattern is thought to emerge or self-organize as a function of the ever-changing constraints placed upon it

Constraints

Defined as the boundaries that limit the movement capabilities of an individual

Three types– Organismic: structural or functional

Body type, wt, ht Psychological, cognitive, emotional

– Environmental:wind, light, flat surface, grassy– Task

Task Constraints

The goal of task: a certain movement Rules that may limit the movement

– One must serve the tennis ball within an area on the baseline

Implements or machines– Using a walker, using weight machines, using a ball

Attractor States

Systems prefer states of stability

When a change in constraints is imposed on a system, its stability is endangered

Deep basins = stable systems = difficult to change

Shallow basins = less stable = more susceptible to change

Phase Shifts

Changes in behavior are the result of a series of shifts

Control parameters– Variables that move the system into new attractor

states: gaining leg strength to perform a skill better

Rate limiters– Constraints that function to hinder or hold back the

ability of a system to change :Adult learner, fear

So what happens when a skill performance needs to change?

Practice strategies need to create instability in a deep attractor basin– As the skill moves through the phase shift, it will

become a combination of the old and new ways– At some point it will be neither the old or new and

performance effectiveness is reduced Eventually through practice, a new attractor

state is formed, and eventually a new deep basin

Key Point

Movement patterns prefer state of stability

New movements self-organize and emerge with phase shifts where attractors stabilize and destabilize as a function of the control parameters

Practical Application

Explain how orthotics function from a dynamic system perspective

Exit Slip

How do the recall and recognition schema work together?

How are phase shifts indicative of behavioral change?